Information on a living body such as pulsation and blood pressure (hereinafter referred to as “biological information”) is measured conventionally by attaching a measurement apparatus such as a sphygmomanometer cuff onto a living body. However, the method of measuring biological information of a subject with a measurement apparatus attached onto a living body sometimes may not accurately measure the biological information because the subject (such as a patient) is aware of the presence of the attached measurement apparatus.
Therefore, a number of contactless biological information measurement apparatuses that measure biological information without needing to be attached to a living body (see for example Japanese Patent Laid-Open No. 2005-270570, No. 2001-187032, and No. 7-241288) have been proposed. For example, a contactless blood-pressure measurement apparatus has been proposed that applies an electromagnetic wave to a living body and detects the electromagnetic wave (reflected wave) scattered from the surface of the living body to measure the blood pressure. Also, a contactless blood-pressure measurement apparatus has been proposed that applies an ultrasound to a living body to measure the blood pressure by determining blood flow using Doppler ultrasound.
However, the biological information measurement apparatuses described above have a problem that the apparatuses may not accurately measure biological information in some situations. In particular, an electromagnetic wave and ultrasound applied to a living body by the biological information measurement apparatuses and the waves reflected by the living body and received by the biological information measurement apparatuses may vary under the influence of the ambient environment such as movement by the subject and obstacles around the subject. Therefore, there is the problem that biological information may not be accurately measured by the biological information measurement apparatuses described above under the influence of the ambient environment.
The technique disclosed herein has been devised in order to address the problem described above and an object of the disclosure is to provide a biological information measurement apparatus and a biological information measurement method capable of accurately measuring biological information.